1. Field of the Invention
The present invention relates to a turning device for a wind turbine rotor that rotates a wind turbine rotor to a desired position when wind speed is low and relates to a wind turbine generator including the same.
2. Description of Related Art
A typical propeller-type wind turbine generator includes a wind turbine rotor having a plurality of wind-turbine blades attached to a rotor head, serving as a center of rotation. The wind turbine rotor is axially supported on a nacelle, which is supported at the top of a tower in a yawable manner; and a gearbox and a generator are disposed inside the nacelle. When the wind turbine rotor rotates by receiving wind, the rotation is sped-up at the gearbox and is transmitted to the generator, and electric power is generated. For an upwind-type wind turbine generator, yaw driving control of the nacelle is carried out so that the rotation center axis of the rotor head (wind turbine rotor) is always orientated windward to efficiently generate power.
In addition, a pitch driving apparatus that turns the wind turbine blades provided on the wind turbine rotor with respect to the rotor head with a driving source, such as hydraulic pressure, to change the pitch angles (angles of attack) of the wind-turbine blades is provided. With such a pitch driving apparatus, the wind-turbine blades are turned to a fine side at which the pitch angle increases when the wind speed is low and to a feather side at which the pitch angle decreases when the wind speed is high. In this way, the generator can efficiently generate power near a desired rotary speed.
With such a wind turbine generator, since the rotation of the wind turbine rotor must be locked at an arbitrary position for maintenance of the wind-turbine blades, pitch driving apparatus, etc., for safety, maintenance is performed in relatively weak wind with a wind speed of approximately 0 to 15 m/s. At this time, if the wind speed is approximately 3 m/s, the wind turbine rotor can idle, a brake can be applied at a predetermined position, and a lock pin can be inserted to lock the rotation of the wind turbine rotor. However, to be able to turn the wind turbine rotor to an arbitrary position in the case where there is absolutely no wind, usually, a turning device using motive power of a small electric motor is provided, as disclosed in US Patent Application, Publication No. 2009/0278359.
In the turning device disclosed in US Patent Application, Publication No. 2009/0278359, a small electric motor is disposed in a gearbox, and the motive power of the electric motor is transmitted to a predetermined rotary shaft of the gearbox via a speed-down gear to rotate (turn) the wind turbine rotor. Specifically, a torque driver is connected to a shaft of an oil pump for gear lubrication, which is attached to the external surface of the gearbox, with an adapter; and the motive power of the electric motor built into the torque driver is transmitted to the rotary shaft of the gearbox via the main shaft of the oil pump and the speed-down gear to rotationally drive the wind turbine rotor.
With the turning device disclosed in US Patent Application, Publication No. 2009/0278359, however, driving-force transmitting parts (input shaft, speed-down gear, bearing, etc.) that transmit the driving force of the electric motor to the wind turbine rotor are designed with relatively large strength such that the strength is achieved in all wind speed ranges (approximately 0 to 15 m/s) in which maintenance is possible.
However, as described above, actually, if there is a wind speed of approximately 3 m/s, the wind turbine rotor can be idled by manually operating the pitch driving apparatus, and thus, in many cases, the turning device does not have to be used. Hence, the turning device is expensive equipment although its frequency of use is low with respect to the operating time of the wind turbine generator, and this has been a cause of the increase in the manufacturing costs of wind turbine generators.
With the turning device according to US Patent Application, Publication No. 2009/0278359, since the driving force of the electric motor is transmitted to the rotary shaft of the gearbox via the relatively expensive gear mechanism, this has also increased the manufacturing costs. Furthermore, if the structure is such that the motive power of the electric motor is transmitted to the wind turbine rotor by the gear mechanism, in the event of a large torque fluctuation caused by the wind turbine rotor due to a gust of wind generated while turning the wind turbine rotor when the wind speed is low, the torque fluctuation will be directly transmitted to the electric motor, and thus, there is a concern that driving-power transmitting parts, such as the electric motor, the gear mechanism, etc., may be damaged.